Electric fuse.



L. W. DOWNES. :ELECTRIC FUSE. APPLrcATloN man MAYH,1913.

Patented Nov. 23, 1915.

LOUIS W. DOWNES, F PROVIDENCE, RHODE ISLAND.

ELECTRIC FUSE.

Specification of Letters Patent. PatentedNOV. 23, 1915.

v Application filed May 17, 1913. Serial No. 768,376.

To all whom it may concern.'

Be it known that I, Louis W. pownns. of Providence, Rhode Island, have invented a new .and useful Improvement in Electric Fuses, which invention is fully set forth in the following specification.

This invention relates to electricv fuses of the type in which, upon blowing or disruption by excessive current, the more eX- pensive main casing with its terminals or other fittings may be retained and repeatedly andeontinuously used by recharging or re- `filling the same with cartridge fuses. Such cartridge fuses, being of relatively light construction, reinforced when in place by the stronger construction of the main and permanent outside case, are relatively inexpensive, thereby enabling the user to recharge ardisrupted or blown lfuse at the minimum expense of purchasing the insert cartridges properly constructed by a manufacturer of such devices.

One object of my invention is to provide a fuse of this character having terminals oi the blade type, but as will be apparent the invention embraces'features of construction also applicable to fuses having other types of terminals.

Another object is to provide a construction which admits of and facilitates the proper introduction of a fresh cartridge and reassemblage of parts in recharging the fuse,

even by unskilled users, thus minimizing` or eliminating risks incidental to relillable fuses the recharging of which requires skill and ingenuity.

Other objects will be apparent from the detailed description and drawing.

The invention may be most fully and readily understoodby reference to the accompanying drawing illustrating what are regarded as preferred embodiments.

Figure 1 is a longitudinal sectional view of oneA end of a fuse which is of similar construction at the other end not shown; Fig. 2 is an end view looking from the left of Fig. 1; Fig. 3 is a sectional View through the Aend cap of the main casing on line of Fig. 1; Fig. t is a similar sectional View through the end cap of the cartridge casing; Fig. 5 comprises detail views of the hollow blade terminal on the cap of the main casing; Fig. 6 comprises detail views of theA blade terminal on the cartridge casina: 7 is a sectional view similar Vthe cap of thecartridge casing of the fuse of Fig. 7.

Referring to Figs. 1 to 6 inclusive, there is a main outside permanent inclosure or casing including'in its structure a tubular part 10, preferably of heavy fibrous insulating material. 11 is a thin steel reinforcing sleeve or annulus tted about the end of tubular part 10 and secured thereto by rivets 12 and 13. The tubular part is closed at its end by a cup-lilre steel cap 14 snugly fitting over the sleeve 11 and rigidly secured 1n place by two oppositely positionedroundheaded screws 15 and 16, each passing through the cap 14: and into screw-headed engagement with openings in the sleeve 11 and casing 10. The cap 14: has perforations 17 (six of such perforations being illustrated in Fig..2) through its end walls constituting vents for the escape of gas from the interior. 18 is a hollow fiat blade terminal projeeting through an elongated opening 19 in the middle of cap 14 and formed by bending a strip of metal, preferably hard-rolled copper', to a U-shape, as shown in Fig. 5, with right angle wings 20 and 21 at the ends of the arms of the U, respectively. lVhen this terminal is in place with relation to the cap 11, the wingsv 20 and 21 lit closely against the inner surface of the end wall of the cap. Hollow rivets 22, 22, passing through the wing 20 and the wall of the cap rigidly fasten one arm of the U-shape blade terminal to said cap, the openings through the tubular rivets providing additional vents for the escape of'gas. up from the wing 21 passes' outwardly through opening in the end wall of cap 1i and on the underside of its end bears slidingly against the outer surface of said end wall, the structure thus described permittingl the two arms of the U-shape hollow blade terminal to Ayieldingly spread apart when such terminal is forced into engagement with the projecting blade terminal of a cartridge fuse introduced within the main casing. As will be understood, the parts thus described in detail are duplicated at the other end of the fuse structure, not shown in Fig. 1, and altogether constitute the outer, main or permanent fuse casing closed at its opposite A tongue 23 bent to yield to the insertion thereinof the blade terminals at the opposite ends of the cartridge fuse.

The cartridge fuse for -removable insertion in the main fuse casing has a tubular casing including in its. structure a relatively thin tubular sheath of insulating material v25, preferably a fibrous material, closely fitting the interior surface of the wall of the main casing 10. A steel cup-like cap 26 tightly fits inside of the end of the sheath 25. After this cap is positioned in the end of the sheath 25, metal disks or washers 27, 27, are placed in circular openings in the wall of the sheath 25 so that they rest against the cap 26 beneath those openings, and solder 2S is applied to fasten each washer to the cap 26 thereby securing said cap in place in the end of the sheath 25. Cap 26 has a series of vent openings 29 (eleven being shown. in the drawing, Fig. 4) for the escape of gas generated in the interior of the cartridge fuse upon blowing or disruption.

30 is a flat blade terminal, formed by a strip of metal doubled upon itself, projecting through elongated opening 31 at the middle of cap 26, and having wings 32, 33 fitting against the interior surface of the end wall of said cap. The terminal wires of suitable fusible links or elements pass through openings in the wings of the terminal 30 and in the cap 26 and are permanently soldered therein, thus securing electrical connection between the blade terminal 3() and the fusible elements. In the drawing two of these terminal wires are shown passing through the openings 87 of the wings 32 and 33., but by proper arrangement more of these fusible elements could, where desirable, be connected in the same manner. The blade terminal 30 may be secured to the cap 26 by riveting `or soldering. The interior of the sheath about the fusible elements 3S and inwardly projecting terminals 34,' 35 is 45 filled with a granular or .finely divided material 39, such as slaked lime, having the well-known function of providing a multitude of interstices for the dissipation and escape of the gas evolved by volatilization of 50 fuse. The construction at one end of the cartridge fuse as hereinbefore described is duplicated at the other end thereof which has not been shown in the drawing.

To refill a fuse of the construction described after it disrupts or blows upon being subjected to an overcharge of current, the screwsl and 16 are first removed, releasing the cap 14 of the mainy casing which is thereupon pulled off, the hollow blade terminal 18 sliding off of the projecting blade terminal 30 of the cartridge fuse in this operation; or it may be that the cartridge fuse is withdrawn with the cap 14 in which case e5 projecting terminal 30 at the opposite end the fusible elements upon blowing of the thereof slides out of the hollow terminal 18 at the other end of the main casing. In either event the blown cartridge fuse is separated from that part to which it remains attached and a. new cartridge fuse introduced into the main casing through the opened end thereof. T he removed cap 14 is then replaced and fastened by screws 15 and 16. In this introduction of a new cartridge fuse the hollow blade terminals 18 of the main casing yield, with slight movement of the tongue 23 in its opening 24, to the introduction of the blade terminals 30 of the cartridge, such yielding action resulting in a slide engagement analogous to that of a knife-blade switch, and affording a firm and extended contacting of surfaces for the transmission of electric current, thus elimi- -nating danger, such as might result from bad contact, of abnormal and undesirable temperature rises with'premature ibloaving of the fuse at les han its maximum rated carrying capacity.

The embodiment illustrated in Figs. 7 and S is substantially the same as that illustrated in Figs. 1 to 6 inclusive except as to features which will be referred to and as to other minor characteristics apparent from an eX- amination of the drawing. The sleeve or ring 40 is made of much lighter metal than 9L the corresponding sleeve or ring 11 of Fig.

1, and it has been found desirable to provide about the inner end of the sleeve L1() an additional telescoping annulus 41 to give additional metal for the formation of adequate thread-holding engagement for the screws 42, a2, passing through the cap 44:, annulus -11, sleeve 40 and into openings in the wall of the tubular portion of the casing, eX- perience having shown that it is vnot advisable to rely very much on the engagement of the screws merely with the .openings .in the ber tube ,for holding the cap in place. The cap 44 is bulged or enlarged at 15 to telescope the annulus 41. To further prevent the force of the expending gases generated within the fuse on blowing thereof from blowing off the end cap of the main casing, a tongue 46 cut in the wall of theI sleeve /10 is bent inward into opening 47 in 11a the wall of the cylindrical tube of the main casing. One of the important features in the structuredescribed is the closing of the ends of the cartridge fuse by caps fitting within 12u the tubular casing thereof, thus eliminating projections from the uniformly cylindrical peripheral surface of the cartridge and enabling the same to fit closely the inner surface of the cylindrical wall. ofv the main 125 casing, practically eliminating or minimizf4 ing air space between these opposing and contacting surfaces. The presence "of an air charged spaceA between these' surfaces j tends lto prevent' proper radiationv of heat 130 when the fuse is in service, with consequent charring, decrease of strength and source of danger. But with the close contact provided the heat is readily transmitted through the two closely fitting walls of the cartridge and main casingand is radiated in the same manner as in the usual single wall fuse. v

To o ain the ydesirable economy in the construction of cartridge fuses, it is desirable to use a fibrous tube having a very thin wall, approximately 31g ofan inchfor fuses of ordinary size. Likewise the caps should be made of very. thin steel. For fastening such wall and caps together and at the same time -avoiding surface projections on the outside which lwould prevent a close fit of the cartridge fuse in \the main casing, and also to securely fasten the parts' together, screws orrivets and other usual methods of fastening are not satisfactory or` practicable. The, washers countersunk in openings through the wall ofthe brous tube ofthe cartridge and .soldered to the cap, constitutes a very simple, economical and eihcient meansof fastening these parts together.

What I claim is 1. The combination of a cartridge fuse in-l cluding in its structure a tubular sheath,a cap closing one end tliereof a blade terminal projecting outward from said cap, with a casing adapted to removably inclose said fuse and including in its structure a tubular part, a cap closing one end thereof, and a U- shaped hollow blade terminal projecting outwardlyfrom and secured to said cap and adapted to yieldingly receive the blade terminal on the cartridge fuse when the latter is inclosed by said casing.

2. The combination of a car'tridge'fuse inl cluding in its structure a tubular sheath, a cap closing one end thereof, a blade terminal projecting outward from said cap, with a casing adapted to removably inclose said fuse and including in its structure a tubular part, a cap closing onelend thereof, and a U-shaped hollow blade terminal having one of its arms rigidly secured to said cap and its other arm movably attached to said cap whereby said hollow terminal is adapted to yieldingly receive the blade terminal on the cartridge fuse when the latter is inclosed by said casing.- v

3. The combination of a cartridge fuse including in its structure a tubular sheath, a cap closing one end thereof, a blade terminal projecting outward from said cap, with 4a casing adapted to removably inclose said fuse and including in its structure a tubular part, a cap closing one end thereof, and a U-shaped hollow blade terminalA having one of its arms rigidly secured to said cap and its other arm movably attached to said cap by a tongue on said arm engaging through an opening in the cap whereby said hollow terminal is adapted to yieldingly receive the blade terminal on the cartridge fuse when the latter is inclosed by said casing.

4. A fuse casing or inclosure including in its structure a tubular sheath of insulating material, a metallic cap fitting inside of and closing one end of said tubular sheath, and a metallic disk countersunk against and sealed to the cap in an opening through the wall of the sheath and thereby securing the cap to the tubular part.

In testimony whereof I have signed this specification in the presence of two subscribing witnesses.

Louis w. nowun's.

Witnesses:

GEORGE W. STEERE, F. G. Davis.

Copies of this patent may be obtained for ve cents each, by addressing the Commissioner of Patents. Washington, D. C. 

